Abstract
Tip-enhanced Raman scattering (TERS) in ångström-scale plasmonic cavities has drawn increasing attention. However, Raman scattering at vanishing cavity distances remains unexplored. Here, we show the evolution of TERS in transition from the tunneling regime to atomic point contact (APC). A stable APC is reversibly formed in the junction between an Ag tip and ultrathin ZnO or NaCl films on the Ag(111) surface at 10 K. An abrupt increase of the TERS intensity occurs upon APC formation for ZnO, but not for NaCl. This remarkable observation is rationalized by a difference in hybridization between the Ag tip and these films, which determines the contribution of charge transfer enhancement in the fused plasmonic junction. The strong hybridization between the Ag tip and ZnO is corroborated by the appearance of a new vibrational mode upon APC formation, whereas it is not observed for the chemically inert NaCl.
Highlights
Tip-enhanced Raman scattering (TERS) in ångström-scale plasmonic cavities has drawn increasing attention
First-principle simulations have suggested that the field confinement reaches even atomic scales,3,4 which is supported by observing characteristic cavity modes of a well-controlled plasmonic dimer in white-light scattering5 and, more recently, by remarkable ångström-resolution Raman imaging in TERS at extremely small gap distances (
In this Letter, we reveal the evolution of TERS intensities and spectra in an atomic-scale plasmonic cavity including transition from a tunneling regime to atomic point contact (APC) formation
Summary
Tip-enhanced Raman scattering (TERS) in ångström-scale plasmonic cavities has drawn increasing attention. In this Letter, we reveal the evolution of TERS intensities and spectra in an atomic-scale plasmonic cavity including transition from a tunneling regime to atomic point contact (APC) formation.
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